With today's widespread use of the Internet as a primary communication medium, standard communication tools are now capable of communicating over a computer network. For instance, telephones, pagers, cell phones, handheld computers, and even fax machines now offer features to allow them to be accessed and controlled from over the Internet via an IP address designation or other network addressing scheme. This ability, whereby various communication devices that traditionally use a circuit-switched telephone network, is known as network telephony, or IP telephony when an IP network is involved.
As a result of network telephony, today's devices have the ability to communicate with one another over networks such as the Internet to share information, or receive data. Furthermore, a user having several communication devices (e.g., a cell phone, laptop and handheld PC) can configure each of these devices to a network using a single alias or identifier, such as a username (e.g., username@b.com). In this way, the user is not limited to communicating with others via a single device, but instead has the ability to communicate via several different devices. Nonetheless, the ability for a user to have several devices “present” on a computer network creates a need for other users to be able to determine the status or state of the users many devices.
Presence refers to the availability, proximity, activity level or operating state of a user on a network. Commonly, the ability for users to monitor each other's presence and generate presence information is a feature offered in connection with computer-executable modules or applications that support network telephony. Such modules or applications are known commonly as presence user agents (PUAs). Examples of typical software applications that operate as PUAs or support PUA-like features include instant messaging applications such as MSN Messenger or AOL Instant Messenger. Both of these applications provide an “available buddy” feature, in which a user of the application can determine whether select users are available for engaging in a communication. The generated by the PUA to create the buddy list, i.e. “John OFFLINE” or “Susan ACTIVE,” is known as presence information, and is generally retrieved and maintained by a presence agent.
According to most conventional network configurations, the presence agent is a dedicated server or computer-executable module that maintains presence information on behalf of a user having one or more computing devices. Typically, the presence agent supports network telephony protocols such as the session initiation protocol (SIP). Users can register their computing devices with the presence agent (e.g., via a registrar module) in order to have their presence maintained and network telephony services facilitated. As such, a user of a first computing device wishing to detect the presence of a user of a second computing device does so by “subscribing” with the presence agent, such as via a SIP SUBSCRIBE message. The presence agent intermediates between the first user, also known as the watcher, and the second user to facilitate the communication of the second user's presence information to the first user.
The ability of a presence agent to accurately determine and maintain presence information for one or more users significantly enhances communication and task completion over the network. Accurate generation of presence information by the PUA operating upon a user's device is also critical for effectively conveying presence. For example, a very mobile user may only be on the network at limited times throughout the day, and from varying network locations. By subscribing as a watcher of this mobile user, it becomes possible for another user to assume the role of a watcher and detect the presence of the mobile user during the limited times at which the mobile user's computing device is actually connected to the network. So, when the mobile user is present, the watcher can correspond instantly with the mobile user via a chat session or videoconferencing call, as opposed to resorting to non-real-time communication such as e-mail messaging. Hence, presence is an especially important factor for facilitating communication between users. Unfortunately, however, conventional PUAs are unable to provide presence information with respect to varying network or operating conditions, and particularly, information sufficient enough to indicate the ability of the device being watched to actually engage in a communication session as a result of a change.
As an example of this phenomenon, consider a scenario where a second user has subscribed with a presence agent as a watcher of a first user. If the first user is in the second users' available buddy list, and the first user's computing device suddenly goes into sleep mode, the second user's buddy list should still indicate that the first user's device is available for communication rather than indicate that the first user's device is “offline.” An indication of offline does not accurately reflect that the first user's device may still be connected to the network and may be available to receive messages. Yet, many PUAs only provide generalized presence information such as “offline” or “unavailable,” and do not account for more intricate presence conditions. Invariably, this phenomenon results in the present agent's inability to convey the presence of the user more accurately to the watcher.
Still further, many PUAs are unable to generate useful presence information for those users that have several devices registered and present upon the network. Current measures for conveying the presence of users having multiple devices simply call for the presence information of each individual device to be presented to the watcher as a compound document, such as an HTML file. As a result, the watcher that receives the compound document indicating the presence information for each device must inherently “guess” which device's presence information most accurately reflects the presence of the user. However, just because a user's mobile phone, pager, laptop, PDA, and desktop computer are all present on the network does not mean the user is using all of them. Indeed, the presence information of the individual devices says very little about the actual presence (e.g., activity or availability) of the user.